What are the muscles known as triceps brachii, biceps femoris and quadriceps femoris named according to? Their:

Correct Answer: B

Rationale: These muscles triceps brachii (three origins, arm), biceps femoris (two origins, thigh), quadriceps femoris (four origins, thigh) are named by origin count ('tri-,' 'bi-,' 'quad-') and location ('brachii' for arm, 'femoris' for femur). Size, shape, fibre direction, or insertions aren't specified. This origin-location convention aids anatomical identification, distinguishing them from size- or shape-based names, reflecting muscle attachment points critical for function.

Correct Answer: A

Rationale: Biceps femoris, a hamstring, acts on the femur and tibia, not the humerus (upper arm). Quadriceps extend the tibia, gluteals move the femur, and biceps brachii flex the radius. This mismatch distinguishes humerus-biceps femoris as non-functional, key to anatomical pairing accuracy.

Correct Answer: A

Rationale: The origin, the muscle's fixed attachment point (e.g., scapula for biceps brachii), moves the least during contraction, anchoring the muscle as it pulls the insertion (movable end, e.g., radius) toward it. The insertion shifts significantly to produce movement. Ligaments , connective tissues stabilizing joints, don't move but stretch slightly under tension. Joints pivot or flex, moving more than the origin. The origin's relative stability, often proximal and attached to larger bones, ensures effective leverage, making 'a' the correct answer in muscle dynamics.

Correct Answer: B

Rationale: The masseter, a powerful jaw muscle, elevates the mandible for chewing, originating from the zygomatic arch and inserting on the mandibular ramus, key in mastication. Swallowing involves pharyngeal muscles (e.g., constrictors), not masseter. Lip movement is orbicularis oris's role. Eye closure is orbicularis oculi's function. Masseter's role in biting and grinding, a primary masticatory action, makes 'b' the correct answer.

Correct Answer: D

Rationale: The sartorius, a long, strap-like muscle from iliac spine to tibia, flexes the hip and knee while rotating the thigh laterally, enabling leg crossing (e.g., tailor's pose). Gluteus maximus extends the hip, piriformis rotates it externally, and gracilis adducts the thigh none fully replicate crossing's combined flexion/rotation. Sartorius's unique diagonal action across hip and knee, dubbed the 'tailor's muscle,' makes 'd' the correct choice.